Changes in potato starch quality during growth

Summary Potato starch quality parameters (amylose concentration, glucose-6-phosphate content and granule size) were analyzed in relation to the harvesting date and tuber size of four cultivars. A significant increase in the glucose-6-phosphate content and granule size of starch was observed during tuber growth, whereas the amylose concentration was constant. Granule size increased markedly, whereas glucose-6-phosphate content showed slightly increasing values with increasing tuber size. Amylose concentration showed no correlation with tuber size. We conclude that the changes in the granule size, glucose-6-phosphate and amylose content of potato starch during growth are independent of each other.     

The effects of colchicine doubling of potato dihaploid X wild species hybrids on eelworm resistance and pollen ‘stainability’

Summary Diploid potato clones (dihaploid x wild species hybrids) and their colchicine doubled, tetraploid counterparts were compared for resistance to eelworm (Globodera rostochiensis andG. pallida) and for pollen ‘stainability’ as an indicator of viability. The responses due to doubling were not uniform. For eelworm resistance, three of the five clone pairs showed no differences; in one pair the tetraploid was significantly more susceptible to one pathotype but not to two others and in the remaining pair, the tetraploid was significantly more susceptible to both pathotypes used. In eleven of fourteen pairs tested for pollen ‘stainability’, the tetraploid had significantly less ‘good’ pollen. In one case, the tetraploid had significantly more ‘good’ pollen. Generally there was sufficient ‘good’ pollen to allow further crossing at the tetraploid level.

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Zusammenfassung Fünf diploide Kartoffelklone, Kreuzungen zwischen anf?lligen Dihaploiden und nematodenresistenten Vermehrungen vonSolanum spegazzinii, S. vernei und einer nicht-beschriebenen, mitS. sparsipilum verwandten peruanischen Art, wurden hinsichtlich ihrer Resistenz mit ihren Colchicin-verdoppelten Gegenstükken verglichen. Tabelle 1 zeigt die verwendeten Nematoden-Populationen (Globodera rostochiensis undG. pallida) zusammen mit der Anzahl gebildeter Zysten. Die Reaktionen gegenüber Verdopplung waren nicht einheitlich; drei der fünf Klonpaare zeigten keine Unterschiede, bei einem der Paare war der tetraploide Teil signifikant anf?lliger gegen einen der Pathotypen, aber nicht gegen zwei andere, und beim letzten Paar war der tetraploide Teil gegen beide verwendeten Pathotypen signifikant anf?lliger. Obwohl die tetraploiden Pflanzen generell ein etwas gr?sseres Wurzelsystem entwickelten als die diploiden und eine gr?ssere Oberfl?che für die Einwirkung der Nematodenlarven boten, liess sich der Schluss ziehen, dass dies nur geringe Auswirkung auf die Feststellbarkeit von Unterschieden zwischen Vertretern der Ploidiepaare hatte. Die Zahl der Eier pro Zyste wurde durch die Resistenz der Pflanzen im Testmaterial nicht beeinflusst. Die Ergebnisse deuten auf gleiche oder niedrigere Grade der Nematodenresistenz durch die Colchicin-Verdopplung. Allerdings deutet die Uneinheitlichkeit der Reaktion darauf hin, dass die Produktion einiger ‘verdoppelter’ Klone mit erh?hter Resistenz doch nicht ganz auszuschliessen ist. Colchicinverdoppelte Klone mit Resistenz im Duplex-Stadium dürften hohen potentiellen Wert als Eltern für weitere Züchtungen auf tetraploidem Niveau haben, vorausgesetzt sie behalten ausreichende Fertilit?t bei. Pollen-‘F?rbbarkeit’ als Indikator der m?nnlichen Fertilit?t wurde in einem gr?sseren Umfang bei Ploidiepaaren, von denen die meistenS. acaule und/oderS. stoloniferum in der Elternschaft hatten, untersucht. Die Ergebnisse zeigt Tabelle 2. In 11 von 14 Paaren hatten die Tetraploiden signifikant weniger ‘gute’ Pollen, in einem Falle signifikant mehr. Generell waren ausreichend ‘gute’ Pollen vorhanden, um weitere Kreuzungen auf tetraploider Ebene zu gestatten. Die Rückkehr auf die tetraploide Ebene via Colchicin-Verdopplung l?sst deshalb einen hohen Anteil verwertbarer Elternlinien für die Erzeugung nematodenresistenter St?mme erwarten.

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Résumé Cinq cl?nes diplo?des obtenus par croisement entre dihaplo?des sensibles aux nématodes et résistants, issus deS. spegazzinii, S. vernei et d'une espèce péruvienne non décrite associée àS. sparsipilum, ont été comparés, pour leur résistance, avec leurs homologues tétraplo?des. Les populations de nématodes (Globodera rostochiensis etG. pallida) qui ont été utilisés sont présentées dans le tableau 1 avec le nombre de kystes nouvellement formés. La réponse donnée par le doublement des chromosomes n'a pas été uniforme; trois des cinq cl?nes n'ont pas montré de différences avec leurs homologues diplo?des; dans un cas le tétraplo?de a été significativement plus sensible à un pathotype mais pas aux deux autres et dans le dernier cas, le tétraplo?de a été significativement plus sensible aux deux pathotypes utilisés. Bien que les plantes tétraplo?des développent généralement un système radiculaire légèrement plus important et présentent une plus grande surface à l'infection par les larves de nématodes que les diplo?des, on conclut que cela a eu peu d'effet au niveau des différences observées entre les deux types de plo?die. Le nombre d'oeufs par kyste n'a pas été affecté sur les plantes résistantes, dans le matériel testé. Ces résultats suggèrent que des degrés similaires ou moindre de résistance aux nématodes peuvent résulter du doublement chromosomique d? à l'effet de la colchicine. Cependant, la non uniformité des réponses fait en sorte que la création de quelques cl?nes tétraplo?des résistants aux nématodes pourrait se faire. De tels cl?nes, ayant des gènes de résistance au niveau duplex, auraient une grande valeur potentielle comme parents pour les hybridations futures au stade tétraplo?de s'ils gardent une fertilité suffisante. La coloration du pollen comme indicateur de fertilité male a été étudiée sur une large gamme de plo?die doublée ayantS. acaule et/ouS. stoloniferum dans la parenté. Les résultats de ces tests sont donnés dans le tableau 2. Dans onze des quatorze paires comparées le tétraplo?de a eu un pollen significativement moins bon que le diplo?de. Dans un cas le tétraplo?de a présenté un pollen significativement meilleur. Cela parait suffisant pour prendre en considération le croisement au niveau tétraplo?de. Par le retour au state tétraplo?de sous l'effet de la colchicine ont peut s'attendre à obtenir de fortes proportions de géniteur valables pour la création de variétés résistantes aux nématodes.

     

Henbane mosaic potyvirus pathogenic to wild and cultivated potato

Summary A virus isolated from severely diseased wild plants ofDatura stramonium in Hungary was identified as a strain of henbane mosaic potyvirus (HeMV) by its host range, vector transmissibility, electron microscopy and serology. This W/H isolate of HeMV induced necrotic local lesions onChenopodium quinoa and characteristic systemic symptoms in species ofDatura, Nicotiana andPhysalis but it was apathogenic to species ofCapsicum, Cucumis andPhaseolus. The virus is transmissible by aphids,Myzus persicae, in a non-persistent manner. Electron microscopy showed that it consisted of flexuous filaments, c. 180×12 nm. In plants ofDatura andNicotiana spontaneously infected by and artificially inoculated with HeMV-W/H, pinwheel structures typical of the potyvirus group were found. Serological examinations confirmed the identity of HeMV-W/H with the standard strain of the virus, HeMV-R. Plants of the potato cultivars Désirée and Gracia, graft-inoculated with HeMV-W/H, were latently infected. Inoculated plants of wildSolanum species responded to the virus with systemic symptoms.     

Seed protein variation within accessions of wild and cultivated potato species and inbredSolanum chacoense

Summary Soluble proteins in seed potato were analyzed by electrophoresis (PAGE). The Index of Variation (IV) was calculated in order to estimate variation within each accession of wild and cultivated potato species andS. chacoense selfed lines. Seeds of 34 accessions representing 14 species from six taxonomic series were analyzed. The IV ofS. chacoense selfed lines decreased from 47.7 in the S₂ to 12.9 in the S₇ generation. The average IV for the self-incompatible diploid species was 41.2, whereas that of the selfcompatible diploid species,S. polyadenium, was 21.3. TetraploidS. tuberosum ssp.andigena andS. sucrense had an average IV of 62.2, which is much higher than that observed in any other diploid species. The naturally selfing speciesS. acaule (4x), and its colchicine-doubled derivative (8x), showed very low variation (IV=7.5). The IV appears to reflect heterozygosity and is affected by the breeding mode and the genetic constitution of diploid parents for derived polyploids.     

Tuber yield and tuber quality of several potato cultivars as affected by seasonal high temperatures and by water deficit in a semi-arid environment

Summary The effects of high temperatures and water deficit on potatoes were investigated under field conditions. Nine cultivars and one un-named seedling were grown in the spring and in the summer under high temperatures. In both seasons the cultivars were grown under 3 water regimes: adequate water supply, moderate water deficit, and severe water deficit that were achieved by a modification of the single line source sprinkler irrigation system. Severe drought reduced tuber yields in both seasons. Moderate tolerance to a moderate water deficit in the spring season was exhibited by Draga, Désirée, and Monalisa. Late and intermediate cultivars produced high tuber yields in the spring season, and early cultivars had relatively smaller yield losses in the summer. The extent of tuber disorders, sprouting, rotting and malformation, varied considerably. High temperatures enhanced sprouting, rotting and malformation and drought may enhance sprouting and malformation. This investigation was supported by a grant from the Ministry of Foreign Affairs, Technical Assistance Department, Netherlands.     

Effects of heat tolerance on expression of resistance toPresudomonas solanacearum E. F. Smith in potato

Summary Twelve potato clones with different genetic background for resistance to bacterial wilt and adaptation were tested for resistance to a race 1 and a race 3 isolate of the pathogen at three locations in the Philippines representing different ranges of ambient temperature. The results showed that the genes for heat tolerance are crucial for resistance. Stability analysis indicated that clones with both resistance and heat tolerance genes displayed higher and more stable resistance to the race 1 isolate than those clones having only resistance genes. The latter group tended to have higher values of both regression of disease index on environmental index and deviation from the regression in the stability analysis. Host — pathogen interaction effects were found to be statistically significant but small compared to main effects of isolates and clones. The involvement of genes with different effects on wilt resistance is discussed. Introduction     

Susceptibility assessment of potato cultivars toFusarium dry rot species

Summary The susceptibility of 43 commercially available potato cultivars to dry rot caused byF. sulphureum, F. solani andF. oxysporum under similar conditions was examined over two years. The cultivars reacted with differing levels of resistance to the dry rot species.F. sulphureum was more aggressive than the other two species and the resistance to each species was independent. The overall cluster analysis classified the cultivars into six groups. Saturna, in an individual group, is the most resistant variety to all tested species, and also toF. surphureum. Panda, Fregate, Folva, Arian and a few others in a group are resistant toF. solani. AlthoughF. oxysporum was the least pathogenetic, almost half of the cultivars are included in a resistant group to this species. There was little correlation between the rank orders of susceptibility of the cultivars to the two main pathogens.     

Effects of soil-borneRhizoctonia solani Kühn on yield and quality of ten potato cultivars

Summary The effects of soil-borneRhizoctonia solani on yield and quality of potato were studied by an extensive individual plant sampling procedure. From 1983 to 1986, stem canker and stolon pruning were examined in 10 768 plants growing on a sandy soil. Tuber yield and quality and haulm yield per plant were also recorded. The degree of attack byR. solani depended on the cropping frequency of potato. Severe and very severe stem and stolon attacks decreased fresh yield, dry matter yield and dry matter content of tubers and increased the number of deformed and small tubers, whereas the effect on haulm yield and stem number was small. Potato cultivars differed in susceptibility toR. solani, but yield response did not differ significantly between cultivars at the same levels of stem and stolon infection.     

Extreme resistance to infection by potato virus X in genotypes of wild tuber-bearingSolanum species

Summary Clones derived from thirty-one different accessions (nineteen of Argentine origin) belonging to eightSolanum species were screened for resistance to infection by potato virus X strain cp (PVX cp) by mechanical inoculation of plantlets that had been micropropagated in vitro. Estimates of PVX multiplication obtained by enzyme linked immunosorbent assay and slot blot nucleic acid hybridization allowed the identification of resistant clones derived from five accessions belonging toS. commersonii S. oplocense, S. sparsipilum andS. tuberosum andigena. Resistant genotypes supported PVX concentrations 5 to 15 times smaller than did the susceptible control cultivar Spunta. Graft inoculation test confirmed the presence of extreme resistance similar to that conferred by the ‘immunity’ gene X¹ (also called RX_act).     

Identification of potato interspecific hybrids resistant toVerticillium wilt and determination of criteria for resistance assessment

Summary Verticillium dahliae causes potato (Solanum tuberosum) early dying disease. Interspecific hybrids containingS. tuberosum, S. berthaultii, S. bukasovii, S. chacoense, S. gourlayi, S. sparsipilum andS. tarijense were identified with resistance toV. dahliae. Clones were grown in replicated trials for three years in a plot containing approximately 50 colony forming units (cfu)V. dahliae per g soil. Clones were evaluated for vine maturity, early dying symptoms and stem colonization. Five resistant 2x clones were identified with early maturity and low levels of stem colonization. A single maturity score and one disease score, each obtained in mid-August, were sufficient to distinguish among clones. An effective threshold level for considering a stem to be infected was determined to be 25 cfu/100 μl sap. Early dying symptoms did not correlate strongly with stem colonization. Numerous stems must be sampled when making resistance assessments. The average cfu/100 μl sap correlated strongly with the number of infected stems.     

The development of mature plant resistance in four potato cultivars against aphid-inoculated potato virus YO and YN in four potato cultivars

Summary Field-grown potato plants of cvs King Edward, Record, Maris Piper and Désirée were inoculated on seven different dates during the growing season of 1987 and 1988 with either potato virus Y^O (PVY^O) or PVY^N, using three viruliferous peach-potato aphids (Myzus persicae) per plant. In each cultivar, the proportion of progeny tubers infected with PVY^O or PVY^N was high in plants inoculated during the four weeks following emergence, the proportion declining to zero or close to zero in the subsequent 4–6 wks.     

In vitro bioassays for salinity tolerance screening of potato

Summary Three in vitro bioassays (single-node cutting, root tip segment and microtuberization) gave similar results in ranking the salinity (NaCl) tolerance of several potato genotypes (Solanum spp.) and were verified by tuber yield criteria in a field lysimeter trial with salinized irrigation water. Salinity stress consistently depressed growth in the single-node cutting and root tip segment bioassays, reduced microtuber yield in the microtuberization bioassay and decreased tuber yield in field lysimeters. The single-node cutting bioassay was simpler to perform than the root tip segment and microtuberization bioassays and did not exclude certain genotypes as did the microtuberization bioassay. The single-node cutting bioassay can be recommended as a substitute for more labour-intensive and costly field assessments of salinity effects of yield.     

Protein,calcium, and iron content of wild and cultivated species ofEchinochloa

Two species ofEchinochloa millets and their direct wild ancestor species were analyzed for proximate composition, and amino acid, calcium, and iron content. Additionally, lactate polyacrylamide gel electrophoresis (PAGE) was performed to separate and resolve prolamin polypeptide present in the wild and domesticated species. The protein, calcium, and iron content of the four species were comparable to or greater than in other major cereals. Calcium was higher in each of the wild species than their domesticated counterpart. Essential amino acid values for the three species analyzed were generally higher than the FAO/WHO standards, except for lysine. Densitometric analysis of lactate PAGE gels revealed that the domesticated species contained prolamin polypeptides that were either absent or present in smaller amounts in the wild species. The results indicate a wide variation in the content of examined nutrients and suggest that there is opportunity for improvement in the nutritional value of theEchinochloa millets via selective crossbreeding of wild and domesticated species.     

Verification of sap flow by heat balance method on three potato cultivars

Summary A heat balance method for measuring sap flow in actively growing plants was tested on three potato (Solanum tuberosum L.) cultivars Monona, Norchip and Atlantic. The method is based on applying a known heat source to the stem of an intact plant: by measuring the axial and radial heat dissipation the magnitude of sap flow can be quantified. The technique shows promise as 24 h accumulated sap flow measurements were highly correlated (r²=0.935, n=36) with gravimetric measurements of transpiration and produced an average root mean square error (RMSE) of 20 g d⁻¹. The accuracy of the method improved as daily accumulated flow increased. Under low daily flow rates overall RMSE increased, supporting the need for a heat storage term in the heat balance equation. Short term flow rates were less significantly correlated (r²=0.764, n=1572) and produced an average RMSE of 2.89 g h⁻¹. Identification of these short term flow rates during high flow periods may be difficult. The presence of water potential gradients and the likelihood of re-hydration during high flow events may have also affected the short term performance of the method. At low flow rates, many different errors may be introduced.     

Cryopreservation of potato shoot tips by encapsulationdehydration

Summary Potato shoot tips excised from 2-week-old in vitro nodal cuttings were cryopreserved after encapsulation in alginate beads. Encapsulated shoot tips were first precultured in sucroseenriched media, dried over silica gel, and rapidly cooled in liquid nitrogen. After slow rewarming in air at room temperature, alginate beads were transferred to solid culture medium for shoot tip recovery. After cooling in liquid nitrogen, shoot yield depended on preculture duration, sucrose concentration and water content of beads. Survival rates above 60% were obtained for each cultivar tested.     

Soluble proteins and isoesterases as taxonomic markers tested on nine wildSolanum species and eight Slovakian potato varieties

Summary Attempts have been made to differentiate 9Solanum species and 8 Slovakian cultivars ofS. tuberosum using soluble proteins, isoesterases and antigenic properties of tuber proteins. Soluble proteins were shown to possess the highest diagnostic value in discriminating between individual species and varieties.S. brevidens of the subsectionEstolonifera deviated from the rest of the species belonging to the subsectionPotatoe. The electrophoretic profiles and immunological responses of individual species only partially correlated with their taxonomic positions. The highest similarity was observed between the pairs of speciesS. bulbocastanum, S. stenotomum, S. maglia-S. phurea andS. gourlayi-S. vernei. It was possible to differentiate also between individual potato cultivars or between their groups according to both soluble protein and isoesterase patterns.     

Screening potato cultivars for common scab of potato in a naturally infested field

Summary Twenty seven cultivars of potato were screened for common scab grown in a commercial field in two successive years (1996–97 and 1997–98). Eight cultivars were least susceptible and the others ranged from medium susceptible to very highly susceptible. None of the cultivars was resistant. Most showed a stable resistance reaction in both years.     

Assessing potato cultivars in Tunisia for susceptibility to leak caused byPythium aphanidermatum

Summary The susceptibility of 21 potato cultivars to leak (watery wound rot) caused byPythium aphanidermatum was compared. Whole tubers were inoculated after wounding by dipping into a water suspension of 10³ oospores/ml and incubated for 3 days at 25°C. The mean penetration of tissue calculated from the recording of lesion width and depth and the qualitative assessment of rot extension were highly correlated. For 10 of 12 cultivars tested at least twice, consistent reactions were obtained: cvs Korrigane. Superstar, Safrane and Yesmina were moderately susceptible, whereas Atlas, Diamant, Mondial, Obélix, Spunta and Timate were susceptible to highly susceptible. Tubers originated from two locations and/or two cropping seasons: thus, the performance of these cultivars under different production conditions reveals a satisfactory level of agreement with the test. Moreover, ratings assigned are supported by field or store observations.     

Effect of functional female and male fertilities on crossability in diploid potato breeding

Summary Functional female fertility (FFF) and functional male fertility (FMF) were studied in diploid potato clones, includingS. tuberosum haploids, F₁ hybrids between haploids and otherSolanum species, and in progenies from subsequent hybridisations. The results of 402 crosses between 91 diploid potato clones revealed that 60% of all genotypes had low levels of FFF as well as low levels of FMF regardless of their origin and degree of hybridity. Failed crosses (without any fruits at all) and those with a low level of success (with less than 3 seeds per pollinated flower) constituted 69% of all studied crosses. Most of these had resulted from parents with low levels of FFF and FMF, and these two characteristics were expressed independently. Functional female fertility affected crossability behaviour no less than FMF, therefore both FFF and FMF should be controlled in diploid potato clones involved in breeding. Reliable FFF and FMF estimates can be based only on crossing results. The coefficient of multiple correlation between seeds per pollinated flower in crosses and FFF and FMF estimates of the parental clones was 0.80 (P<0.01). Hence the compilation and analysis of the results of diploid potato crosses allow a reliable assessment of FFF and FMF and consequently the prediction of crossability with a degree of sufficient accuracy.